1. Field of the Invention
The present invention relates to improvements in a winding mechanism that retains a flexible sheet material in a state in which the sheet material can be pulled out.
2. Related Background Art
A tonneau cover device may be typically attached to a vehicle such as a van or a truck having a cargo space. The tonneau cover device includes a tonneau cover that is typically made of a flexible sheet material and a winding mechanism that can wind the tonneau cover around a winding shaft in a cover storage box. The tonneau cover that is wound around the winding shaft can be pulled out from the cover storage box when it is required to cover the cargo space. The tonneau cover device is provided with a braking device inside the cover storage box to control movements of the tonneau cover when the tonneau cover is wound. The braking device is typically provided with a spring member that flexibly contacts the tonneau cover to apply a braking force to the tonneau cover. However, in the conventional structure, the braking device applies a braking force to the tonneau cover not only when the tonneau cover is wound but also when it is pulled out. Another braking device applies a braking force to the tonneau cover when the tonneau cover is wound and in an initial stage of a pull-out operation in which the tonneau cover is pulled out from the cover storage box. With such a braking structure, the resistance to the pull-out operation may be reduced, but the tonneau cover cannot be pulled out stably due to the braking force applied in the initial stage of pull-out operation. Furthermore, the braking force applied to the winding shaft is apt to change according to the amount of the tonneau cover that is wound (or pulled out), which makes it particularly difficult to control the winding speed at constant.